JP5121141B2 - Polytrimethylene terephthalate composition and method for producing the same - Google Patents

Abstract

A polytrimethylene terephthalate composition comprising polytrimethylene terephthalate, wherein said polytrimethylene terephthalate comprises 50 mol% or more of trimethylene terephthalate repeating units, wherein the composition satisfies the following requirements (A) to (C): (A) b* value is -5 to 25, wherein the b* value is obtained after heating at 180 DEG C for 20 hours under an air atmosphere; (B) each of acrolein and allyl alcohol in a solution which has the composition dissolved in hexafluoroisopropanol is not more than 20 ppm/composition; and (C) degree of crystallinity Xc thereof is 0-40%, wherein the degree of crystallinity Xc is represented by <DF>Xc = ä rho c x ( rho s - rho a)ü/( rho s x ( rho c - rho a)ü x 100(%) </DF> wherein rho a:   amorphous density = 1.300 g/cm<3> rho c:   crystal density = 1.431 g/cm<3> rho s:   density of composition(g/cm<3>).

Description

The present invention relates to a method for producing a polytrimethylene terephthalate composition. More specifically, the present invention is excellent in color tone even when performing melt molding such as melt spinning and extrusion molding, and always gives a molded product having the same color tone. The present invention relates to a method for producing a polytrimethylene terephthalate composition.

  Polytrimethylene terephthalate (hereinafter sometimes abbreviated as “PTT”), when made into fibers, has properties similar to nylon fibers such as soft texture, excellent elastic recovery and easy dyeability due to low elastic modulus. In recent years, it has become an epoch-making fiber having properties similar to polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”) fibers such as wash and wear, dimensional stability, and yellowing resistance. Taking advantage of this, it has begun to attract attention as a material that can be applied to carpets and clothing. Moreover, PTT is excellent by utilizing characteristics not found in nylon such as low moisture absorption and yellowing resistance, and characteristics not found in polybutylene terephthalate (hereinafter sometimes abbreviated as “PBT”) such as easy moldability and good appearance. It is also expected to become a molding material.

  In the future, in order to further expand the applications of PTT by taking advantage of these features, molded products such as fibers, injection molded products, and extrusion molded products with excellent whiteness and uniform color without unevenness. There is a demand for a polymer capable of obtaining a polymer, and there is a need for a method capable of producing the polymer with high industrial productivity.

  Usually, PTT is a lower alcohol diester of terephthalic acid such as terephthalic acid (hereinafter sometimes abbreviated as “TPA”) or dimethyl terephthalate (hereinafter sometimes abbreviated as “DMT”), and trimethylene glycol (hereinafter referred to as “TMT”). "TMG") is heated in the presence of a catalyst such as a non-catalyst or a metal carboxylate, titanium alkoxide, etc. to carry out a transesterification reaction or a direct esterification reaction, and bis (3-hydroxypropyl) ) After obtaining terephthalate (hereinafter sometimes abbreviated as “BHPT”), the BHPT is reacted in the presence of a catalyst such as titanium alkoxide or antimony oxide in the molten state to produce TMG as a by-product. It can be obtained by carrying out a polycondensation reaction withdrawing outside.

In order to obtain fibers and molded products with excellent whiteness and uniform color and uniformity, it is necessary to increase the whiteness and uniformity of the polymer and to suppress coloring due to thermal history such as drying and melting There is. However, compared with polyesters such as PET and PBT, PTT has a problem that it tends to be colored when heat treatment such as drying and crystallization is performed or when it is melt-molded. Normally, PET is hardly colored even when it is dried at a high temperature of 180 ° C. or melt-molded, whereas PTT is easily colored yellow. The cause of this is not clear, but it is considered that PTT is easily decomposed by heat and that the compound produced by the heat decomposition and the functional group in the polymer are likely to cause coloration, which is characteristic of PTT.
In order to increase productivity and suppress whiteness unevenness, it is desirable to perform so-called “continuous polymerization” in which raw materials are continuously supplied to a reactor, polymerized in a molten state, and continuously extracted. .

As a technique for continuously polymerizing PTT, there has been proposed a method for suppressing thermal decomposition by controlling the temperature of the heating medium so as not to exceed 300 ° C., preferably 290 ° C., in order to control the wall temperature of the polymerization reactor. ing. For example, see Patent Document 1 described later.
In addition, in a continuous polymerization method using a plurality of reactors, a technology for reducing the amount of by-products such as acrolein and increasing the molecular weight of the resulting polymer by setting each reactor to an appropriate temperature and residence time. Has been proposed. For example, see Patent Documents 2 and 3 described later.
However, according to the study by the present inventors, when the above technique is used, although thermal decomposition can be suppressed to increase the molecular weight or reduce the generation amount of acrolein or the like, it is colored when melt-molded. It is difficult to obtain difficult polymers.

As a technique for suppressing the coloring of the polymer, improvement by a heat stabilizer has also been made. For example, see Patent Document 4 described later.
However, when polymerization is performed using a heat stabilizer or the like, it is possible to surely obtain a polymer with good color tone, but it is not possible to suppress coloration by melt molding or heat treatment at a high temperature, but rather a heat stabilizer. The product itself is colored, and the color tone of the obtained molded product is deteriorated.
In addition, a technique has been proposed in which a tin catalyst is used as a polycondensation catalyst and a polymer having a low yellowness is obtained by adding a pigment. For example, see Patent Document 5 described later.
In addition, as a polycondensation catalyst, a technique for obtaining a polymer with excellent thermal stability and good color tone by using a special titanium catalyst having a specific arrangement with atoms in the vicinity has been proposed. For example, see Patent Documents 6 and 7 described later.

However, according to our study, the tin catalyst has high activity, so that it accelerates the polymerization and at the same time promotes the decomposition of the produced polymer. For this reason, the polymer is easy to be colored, and in order to suppress this, the pigment is made inconspicuous. Therefore, even if a polymer having a good color tone is obtained, the color tone of the polymer deteriorates when subjected to a thermal history such as drying or melt molding. In addition, when a special titanium catalyst is used, the yellow color is reduced, but the polymer is darkened, and the resulting molded product cannot be said to have a very good color tone.
In addition, a technique for performing solid phase polymerization after performing melt polymerization has also been proposed. For example, see Patent Document 8 described later.

In this technique, the pellets are heated at a high temperature for a long time, so that the polymer is highly crystallized. As a result, a large amount of powdery polymer is generated during polymerization or when conveying the polymerization pellets, or unmelted portions are formed during molding. All of these become defects in the molded product when formed into fibers, films, and bottles. Further, since polymerization is performed in the form of pellets, it is extremely difficult to make the degree of polymerization and color tone between the pellets and the colorability during heating uniform. Furthermore, since it is necessary to solidify and crystallize once after melt polymerization and perform polymerization in a solid phase for a long time, a large-scale facility is required and productivity is deteriorated.
Thus, with the conventional PTT manufacturing technology, it is not possible to obtain an excellent polymer that can give a molded product having an excellent color tone and can be manufactured by continuous melt polymerization with good industrial productivity. In addition, since it is a phenomenon unique to PTT that it is easy to be colored due to thermal history, it is possible to obtain a polymer for obtaining a molded product having an excellent color tone even by simply applying conventional polyester manufacturing techniques such as PET and PBT. I can't.

: US Pat. No. 6,277,947 : International Publication No. 2000/158980 : International Publication No. 2000/158981 : International Publication No. 98/23662 : JP-A-5-262862 : JP 2000-159875 A : JP 2000-159876 A : US Pat. No. 6,403,762

  An object of the present invention is to provide a polymer composition for obtaining a fiber or molded article having excellent whiteness and uniform color without unevenness by melt molding that is dried or melted at a high temperature, and the polymer composition Is to provide a method that can be produced industrially with high productivity.

As a result of intensive studies, the present inventors have surprisingly found that the average residence time in the piping and equipment from the time when the degree of polymerization is increased in a reduced pressure or inert gas stream to cooling and the inner wall surface temperature of the equipment. Is found to be an industrially highly productive PTT composition that is excellent in color tone and can always give a molded product of the same color tone even when melt molding is performed. Completed the invention.
That is, the present invention is as follows.

(I) 50 mol% or more is composed of repeating units of trimethylene terephthalate and satisfies the following requirements (A) to (C), and the remaining 50 mol% or less is composed of other copolymer components. A process for making a polytrimethylene terephthalate composition comprising:
Using one or more reactors, raw materials, intermediates and low polymerization degree polymers were continuously added to the reactor and reacted in a molten state to continuously produce polytrimethylene terephthalate. Including the continuous withdrawal of the polymer , including the residence time in the flow path in the piping and equipment through which the polymer passes after leaving the final polymerization reactor where the polymer in the molten state undergoes polycondensation at reduced pressure. The polytrimethylene is characterized in that the average residence time until cooling and solidification is 0.01 to 50 minutes, and the temperature of the inner wall surface of the pipe and / or the apparatus in contact with this is 290 ° C. or less A method for producing a terephthalate composition.
(A) The b * value is −5 to 25 and the b * value after heating at 180 ° C. for 20 hours in an air atmosphere is −5 to 25;
(B) Acrolein and allyl alcohol in a solution of the composition dissolved in hexafluoroisopropanol are both 20 ppm / composition or less; and (C) Crystallinity Xc is 0 to 40%.
Here, the crystallinity Xc is
Xc = {ρ _c × (ρ _s −ρ _a )} / {ρ _s × (ρ _c −ρ _a )} × 100 (%)
Represented by
ρ _a : Amorphous density = 1.300 g / cm ³
ρ _c : crystal density = 1.431 g / cm ³
ρ _s : density of the composition (g / cm ³ )
(II) The method for producing a polytrimethylene terephthalate composition according to (I), wherein the intrinsic viscosity [η] of the obtained polytrimethylene terephthalate composition is 0.4 to 3.0 dl / g.
(III) Polytrimethylene terephthalate according to (I) or (II), wherein the carboxyl end group concentration of the polymer that increases from the time of leaving the final polymerization reactor until it is cooled and solidified is in the range of 0 to 30 meq / kg A method for producing the composition.
(IV) A pellet containing the polytrimethylene terephthalate composition obtained by the production method according to any one of (I) to (III).
(V) A molded article having a b * value of -5 to 25, comprising the polytrimethylene terephthalate composition obtained by the production method according to any one of (I) to (III).

It is a schematic diagram which shows the outline of the polymerization machine of this invention which superposes | polymerizes from a raw material. It is a schematic diagram which shows the outline of the polymerization machine of this invention which superposes | polymerizes from a low polymerization degree polymer.

Hereinafter, the present invention will be described in detail.
The PTT of the present invention is a PTT composed of 50% by mole or more of trimethylene terephthalate repeating units. Here, PTT is a polyester having terephthalic acid as an acid component and trimethylene glycol (also referred to as 1,3-propanediol, hereinafter sometimes abbreviated as “TMG”) as a diol component. PTT may contain one or more other copolymer components at 50 mol% or less. Examples of the copolymer component contained include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 3,5-dicarboxylic acid benzenesulfonic acid tetrabutylphosphonium salt, 3,5-dicarboxylic acid benzenesulfonic acid tributylmethylphosphonium salt, 1,4-butanediol, neopentyl glycol, 1,6-hexamethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, adipic acid, dodecanedioic acid, 1,4-cyclohexanedicarboxylic acid, etc. Examples include ester-forming monomers. In order to bring out the characteristics of PTT such as elastic recovery property, wash and wear property, dimensional stability, easy formability and good appearance of the molded product, the trimethylene terephthalate repeating unit is preferably 70 mol% or more, preferably 80 mol%. % Or more is more preferable, and 90 mol% or more is particularly preferable.

The term “PTT composition” of the present invention is also used to indicate a single PTT itself in which both acrolein and allyl alcohol in the requirement (B) are 0 ppm, and further acrolein and allyl alcohol. And PTT compositions containing cyclic or linear oligomers, monomers such as DMT, TPA, TMG, and various additives in addition to the PTT alone or the PTT composition. Shall.
The PTT composition of the present invention needs to have a b * value of -5 to 25 and a b * value of -5 to 25 after heating at 180 ° C for 20 hours in an air atmosphere.

  According to the study by the present inventors, in order to increase the whiteness of a molded product, not only the whiteness of the PTT composition used for molding is excellent, but also the PTT composition such as drying at high temperature or melt molding. It was found that it is important that coloring is difficult when heated. Although the cause is not clear, it is considered that the coloring is caused not only by the decomposition of the polymer itself upon heating but also by some coloring-causing substance or functional group contained in the PTT composition in advance. As an index of ease of coloring when heated, the color tone after heating the PTT composition at 180 ° C. for 20 hours in an air atmosphere can be used. Therefore, in the present invention, by setting the composition and b * after heating the composition within the above ranges, a molded article having excellent whiteness can be obtained for the first time. The b * value is more preferably from −4 to 21, more preferably from −3 to 18, particularly preferably from −2 to 16, and most preferably 0.

  In order to make it easy to develop a desired color when the molded product is colored with a dye or pigment without darkening the resulting molded product, the L value of the composition and the composition are set as described above. The L value after heat treatment is preferably 70 or more, more preferably 75 or more, and still more preferably 80 or more. There is no particular upper limit on the L value, but it is usually 100 or less.

  In the present invention, both acrolein and allyl alcohol in a solution obtained by dissolving the composition in hexafluoroisopropanol must be 20 ppm / composition or less. By doing in this way, it becomes possible to raise the whiteness of the molded product obtained. There is a great correlation between the amount of these substances and the coloration during heating. Although the cause is not certain, it is expected that these substances are coloring-causing substances themselves or substances that increase or decrease in the same manner as coloring substances. Moreover, since the said substance worsens a working environment, it is very desirable also in manufacturing a molded article to reduce the content in a composition and to suppress discharge | release from a composition. Acrolein and allyl alcohol are preferably 15 ppm / composition or less, more preferably 10 ppm / composition or less, particularly preferably 5 ppm / composition or less, and of course 0 ppm / composition is most preferred.

Furthermore, in the present invention, the crystallinity Xc of the PTT composition needs to be 0 to 40%.
Here, the crystallinity Xc is
Xc = {ρ _c × (ρ _s −ρ _a )} / {ρ _s × (ρ _c −ρ _a )} × 100 (%)
Represented by
ρ _a : Amorphous density = 1.300 g / cm ³
ρ _c : crystal density = 1.431 g / cm ³
ρ _s : density of the composition (g / cm ³ )
It is.
By making such a crystallinity, the composition can be prevented from becoming brittle, and a PTT-specific problem that a powdery polymer is generated when transported by a pneumatic or feeder (this problem is caused by other PET and It does not occur in PBT etc.). The degree of crystallinity is more preferably 0 to 35%, still more preferably 0 to 30%.
The crystallinity referred to here is an average value in one pellet. Preferably, when the pellet is cut and divided into a surface layer and a central portion, the crystallinity falls within the above range in all portions. Is preferred. Further, the difference in crystallinity between the surface layer and the central portion is preferably 40% or less, more preferably 30% or less, and particularly preferably 20% or less.

  The intrinsic viscosity [η] of the PTT composition of the present invention is preferably in the range of 0.4 to 3.0 dl / g. In consideration of obtaining fibers and molded articles having practical strength, 0.4 dl / g or more is preferable. Considering the difficulty of melt molding due to an increase in melt viscosity, it is preferably 3.0 dl / g or less. The intrinsic viscosity [η] is preferably in the range of 0.5 to 2.5 dl / g, more preferably in the range of 0.6 to 2.0 dl / g.

  In addition, the carboxyl end group concentration is desirably 50 meq / kg or less in order to prevent hydrolysis even when molded in an insufficiently dried state or to improve the weather resistance of the molded product. . The carboxyl end group concentration is preferably 30 meq / kg composition or less, more preferably 20 meq / kg composition or less, and particularly preferably 10 meq / kg or less. The lower the carboxyl end group concentration, the better.

  The form of the PTT composition of the present invention is usually a pellet, but may be a powder depending on the application. Moreover, it is good also as a fiber, a film, a molded object, and its intermediate body by shape | molding a PTT composition directly after superposition | polymerization. In the case of pellets, the average weight is preferably 1 to 1000 mg / piece. By setting the particle size to have this average weight, it becomes easy to extrude uniformly with a molding machine, the handling property at the time of transportation, drying and spinning of pellets is improved, and the drying speed is increased. The average weight is more preferably 5 to 500 mg / piece, particularly preferably 10 to 200 mg / piece. The shape of the pellet may be any of a sphere, a rectangular parallelepiped, a cylinder, and a cone, but considering the handleability, the length of the longest part is preferably 15 mm or less, more preferably 10 mm or less, and 5 mm or less. More preferably.

Next, a method for producing the PTT composition of the present invention will be described.
Usually, PTT heats a lower alcohol diester of terephthalic acid such as terephthalic acid or DMT and TMG in the presence of a catalyst such as a non-catalyst or a metal carboxylate, titanium alkoxide, and the like, thereby performing an ester exchange reaction or a direct esterification reaction. After obtaining BHPT, the BHPT is heated and reacted in the presence of a catalyst such as titanium alkoxide in a molten state, and a polymer is obtained by polycondensation reaction while extracting by-product TMG out of the system. it can.
In the polymerization method according to the present invention, in addition to the method of polymerizing from the raw materials as described above, an intermediate BHPT or a polymer having a low polymerization degree is heated in a molten state in the presence of a catalyst such as titanium alkoxide. It also includes a method of reacting and obtaining a polymer by polycondensation reaction while extracting by-product TMG out of the system.

It is important that the method of the present invention is a so-called continuous polymerization in which raw materials, intermediates and a low polymerization degree polymer are continuously charged into a reactor and the polymer obtained by polymerization is continuously extracted. By setting it as continuous polymerization, it becomes possible to suppress the quality unevenness of the polymer obtained.
The number of reactors used in the present invention is one or more. However, when polymerization is performed from TMG as a raw material and lower alcohol diester of terephthalic acid or TPA, polymerization is performed from three or more, BHPT or a polymer having a very low polymerization degree. When carrying out, it is preferable to use 2 or more groups.
The polymer obtained by polymerization is extracted from the final polymerization reactor using a gear pump or an extruder, and then discharged from a nozzle through a pipe or the like into a gas such as air or nitrogen, and cooled and solidified in the gas as it is, or It is cooled and solidified by contact with a liquid such as water or a solid such as metal. In order to use the polymer for molding, it is preferable that the polymer is cooled and solidified by contacting with a liquid such as water.

As described above, in order to obtain a molded product having excellent whiteness, not only the whiteness of the polymer composition is excellent, but also the polymer composition is colored when heated such as drying at high temperature or melt molding. It is thought that it is necessary to reduce the amount of any color-causing substance or functional group contained in the polymer. Although this color-causing substance or functional group is thought to be generated along with thermal decomposition, it remains in the polymer because it is extracted out of the system together with TMG generated by the polymerization reaction even if it is somewhat generated in the polymerization reactor. It seems difficult to do. However, in a sealed space such as piping or equipment after leaving the polymerization reactor, it is considered that the polymer will accumulate in the polymer because it is not drawn out of the system, and is sealed in a molten state for a long time. When the polymer placed in the vacant space is heated, it is highly colored.
Therefore, in order to suppress coloring during heating, the average residence time from when the polymer leaves the final polymerization reactor until it is cooled and solidified, and the temperature of the inner wall surface of the piping and / or apparatus in contact therewith are controlled. It is thought that it is very important to suppress thermal decomposition and reduce coloring-causing substances or functional groups in the polymer.

  Here, "device" refers to all devices in the flow path through which the polymer passes from the final polymerization reactor outlet until it is discharged into the gas. For example, a kneading device for kneading additives, a filtration device, a polymer Refers to a gear pump, a single-screw or twin-screw extruder for feeding the liquid from the polymerization vessel. “Piping” refers to piping connecting the final polymerization reactor to these devices and nozzles. If there is a zone in the final polymerization reactor where the degree of polymerization does not increase, this zone is also included.

In the production method of the present invention, the polymer in a molten state after leaving the final polymerization reactor is passed through a pipe or a passage in the apparatus through which the polymer passes after leaving the final polymerization reactor that performs polycondensation under reduced pressure. It is necessary that the average residence time until cooling and solidification including 0.01 residence time is 0.01 to 50 minutes. The average residence time is preferably within 50 minutes considering the coloring of the polymer during heating. The shorter the average residence time, the better, but in practice it is 0.01 minutes or more. The average residence time is preferably 0.02 to 40 minutes, more preferably 0.03 to 30 minutes, and particularly preferably 0.04 to 20 minutes. In addition, it is preferable that the so-called dead space in which the polymer stays for a long time is minimized in the piping through which the polymer passes and the flow path in the apparatus.
If the average residence time can be measured, the value must be within the above range. If the actual residence time cannot be measured, a value obtained by dividing the average residence amount of the pipe and / or the apparatus by the discharge amount per unit time is obtained. It is necessary to be within the above range.

On the other hand, the temperature of the inner wall surface of the pipe and / or the apparatus with which the polymer comes into contact after it leaves the final polymerization reactor and is cooled and solidified needs to be 290 ° C. or lower. Considering a decrease in the degree of polymerization due to thermal decomposition and coloring of the polymer during heating, 290 ° C. or lower is preferable. On the other hand, considering the increase in the viscosity of the polymer due to a decrease in temperature and the difficulty of extraction due to solidification, it is preferably 220 ° C. or higher. The temperature is preferably 225 to 280 ° C, more preferably 230 to 275 ° C, and particularly preferably 235 to 270 ° C.
The temperature of piping and / or the inner wall surface of the apparatus with which the polymer is in contact is preferably as uniform as possible, and is preferably heated by a liquid controlled within the above temperature range so that only a part does not deviate from the above temperature range. Also when using a heater etc., it is preferable to control so that the temperature of the heater surface may be in the above-mentioned range.

  The final polymerization reactor of the present invention includes a vertical stirring reactor, a horizontal stirring reactor having a uniaxial or biaxial stirring blade, a reactor that polymerizes while dropping a polymer along a support, a shelf All the reactors that can increase the degree of polymerization of the polymer, such as a natural flow type thin film polymerization reactor having a flow rate, a thin film polymerization reactor that naturally flows on an inclined plane, and a twin-screw extruder type reactor. Among these, in order to obtain a polymer with a high degree of polymerization capable of obtaining a molded article having excellent strength, the polymer is dropped along a horizontal stirring reactor or support having a uniaxial or biaxial stirring blade. A reactor that is polymerized while being allowed to run is preferred.

  In such a final polymerization reactor, the polymerization is carried out while circulating a reduced pressure or an inert gas. In order to reduce coloring-causing substances or functional groups in the polymer, it is desirable to carry out the polymerization at a reduced pressure. The average residence time in the final polymerization reactor is preferably within 5 hours, more preferably within 4 hours, and particularly preferably within 3 hours.

  In the present invention, it is desirable that the amount of carboxyl terminal groups of the polymer which increases from the time when it leaves the final polymerization reactor until it is cooled and solidified is in the range of 0 to 30 meq / kg. Although it is believed that the carboxyl end groups of the polymer do not cause direct coloration, the amount is an indicator of the amount of color-causing substances or functional groups. A high concentration of carboxyl end groups in the polymer indicates that there are many coloring-causing substances or functional groups, and the resulting molded product is likely to be colored. The increasing carboxyl end group concentration of the polymer is preferably 0 to 20 meq / kg, more preferably 0 to 15 meq / kg, and particularly preferably 0 to 10 meq / kg. Of course, the smaller the better. For the same reason, it is better that the carboxyl end group concentration of the polymer exiting the final polymerization reactor is lower, preferably 0 to 40 meq / kg, more preferably 0 to 20 meq / kg, particularly preferably 0 to 10 meq / kg. kg.

Next, one example of the method of the present invention for producing a PTT composition from a raw material by polymerization is illustrated, but the present invention is not limited to this method.
The PTT production method is roughly classified according to the difference in raw materials, and transesterification of TMG with a lower alcohol diester of terephthalic acid is performed to obtain BHPT, which is an intermediate of PTT, and then polycondensation reaction of the BHPT is performed. After a method for producing a polymer (hereinafter sometimes abbreviated as “transesterification method”), terephthalic acid and TMG are subjected to an esterification reaction to obtain BHPT, the same as in the first method, There is a method of producing a PTT prepolymer by a condensation reaction (hereinafter sometimes abbreviated as “direct esterification method”). Here, BHPT includes those containing terephthalic acid, lower alcohol esters of terephthalic acid, TMG and PTT oligomers in addition to the bis (3-hydroxypropyl terephthalate) itself.

  In the transesterification method, DMT and TMG, which are a kind of lower alcohol diester of terephthalic acid, are transesterified at a temperature of 150 to 240 ° C. in the presence of a transesterification catalyst to obtain BHPT. The molar ratio of the lower alcohol diester of terephthalic acid and TMG when charged is preferably 1: 1.3 to 1: 4, more preferably 1: 1.5 to 1: 2.5. Considering the length of the reaction time, it is preferable that TMG is more than 1: 1.3. On the other hand, considering the length of polymerization time for volatilizing TMG not involved in the reaction, it is preferable that TMG is less than 1: 4.

In the transesterification method, it is necessary to use a transesterification catalyst, and preferable examples include titanium alkoxide represented by titanium tetrabutoxide and titanium tetraisopropoxide, cobalt acetate, calcium acetate, zinc acetate and the like. Of these, titanium tetrabutoxide is preferable because it functions as a subsequent polycondensation reaction catalyst. The amount of the transesterification catalyst is preferably 0.02 to 1% by weight, more preferably 0.05 to 0.5% by weight, still more preferably 0.08 to 0.2% by weight based on the terephthalic acid diester.

In the direct esterification method, terephthalic acid and TMG are esterified at a temperature of 150 to 240 ° C. to obtain BHPT. The molar ratio of terephthalic acid and TMG when charged is preferably 1: 1.05 to 1: 3, more preferably 1: 1.1 to 1: 2. Considering the length of reaction time and coloring, it is preferable that TMG is larger than 1: 1.05. In consideration of the polymerization time for volatilizing TMG not involved in the reaction, it is preferable that TMG is less than 1: 3.
In the direct esterification method, since the proton liberated from terephthalic acid acts as a catalyst, an esterification catalyst is not always necessary, but in order to increase the reaction rate, it is preferable to use an esterification catalyst. Preferable examples include titanium alkoxides typified by titanium tetrabutoxide and titanium tetraisopropoxide. The amount added is preferably 0.02 to 1% by weight, more preferably 0.05 to 0.5% by weight, and still more preferably 0.08 to 0.2% by weight, based on the terephthalic acid used.

The BHPT obtained by the above method is subsequently polycondensed to give a polymer.
The polycondensation is carried out while reacting BHPT at a predetermined temperature under reduced pressure or in an inert gas atmosphere while removing TMG produced as a by-product. The temperature for performing the polycondensation is preferably 230 to 280 ° C. Considering solidification of the reaction product and the length of the reaction time, 230 ° C. or higher is preferable. On the other hand, considering thermal decomposition and the color tone of the polymer, 280 ° C. or lower is preferable. The temperature is more preferably 232 to 275 ° C, further preferably 235 to 270 ° C.

The polycondensation reaction can be performed under reduced pressure or in an inert gas atmosphere. When the pressure is reduced, the degree of pressure reduction is appropriately adjusted according to the sublimation state and reaction rate of BHPT and the polycondensation reaction product. When the polycondensation reaction is performed in an inert gas atmosphere, it is important that the inert gas is sufficiently replaced as needed so that the by-produced TMG can be efficiently removed. In the present invention, the polycondensation reaction is performed under reduced pressure .

For polycondensation of BHPT, it is desirable to use a polycondensation catalyst. If a polycondensation catalyst is not used, the polycondensation time will be long. Preferred examples of the polycondensation catalyst include titanium alkoxides typified by titanium tetrabutoxide and titanium tetraisopropoxide, titanium dioxide, double salts of titanium dioxide and silicon dioxide, antimony compounds such as antimony trioxide and antimony acetate, 2- Examples thereof include tin compounds such as tin ethylhexanoate, butyltin acid, and butyltin tris (2-ethylhexoate). Titanium tetrabutoxide and tin 2-ethylhexanoate are preferred in that the reaction rate is fast and the color tone can be improved. These catalysts may be used alone or in combination of two or more. The amount of the polycondensation catalyst is preferably added so as to be 0.001 to 1% by weight, more preferably 0.005 to 0.5% by weight based on the weight of the polymer to be obtained. It is particularly preferable to add so as to be 0.01 to 0.2% by weight. When the compound used in the process of obtaining BHPT also acts as a polycondensation catalyst, the polycondensation catalyst may be added so that the amount including the amount of the compound is as described above.
When polymerization is carried out from BHPT by a continuous polymerization method, it is preferable to carry out the polycondensation reaction in two or more reactors in order to advance the reaction efficiently, and to change the temperature, the degree of reduced pressure, and the like.

  The PTT obtained by polymerization can be formed into pellets (also referred to as chips), subjected to crystallization and drying steps, and then used for forming. The pellet is obtained by extruding the molten polymer into a strand or a sheet to cool and solidify, and then cutting. In this case, it is necessary to appropriately select the cooling temperature and the time until cooling so as to be within the range of the crystallinity Xc of the present invention. Usually, the molten polymer is extruded into a strand shape or a sheet shape, rapidly put into a coolant such as water, cooled, and then cut. The temperature of the refrigerant is preferably 20 ° C. or less, more preferably 15 ° C. or less, and still more preferably 10 ° C. or less. As the refrigerant, water is preferable in view of economic efficiency and handleability. For this reason, the refrigerant temperature is preferably 0 ° C. or higher. The cutting to form a pellet is preferably performed after cooling and solidifying to 55 ° C. or less within 120 seconds after extruding the polymer.

  In the present invention, the molten polymer can be directly introduced into a spinning machine or an extrusion molding machine without being formed into pellets, and then cooled and solidified to obtain a molded product. The present invention includes such a case, and in this case as well, the average residence time from the time of leaving the final polymerization reactor until cooling and solidification is 0.01 to 50 minutes, It is necessary that the temperature of the inner wall surface of the apparatus is 290 ° C. or lower.

In the present invention, various additives such as a matting agent, a heat stabilizer, a flame retardant, an antistatic agent, an antifoaming agent, a color adjusting agent, an antioxidant, an ultraviolet absorber, a crystal nucleating agent, an increase agent are added as necessary. In some cases, a whitening agent or the like is copolymerized or mixed. These additives can be added at any stage of the polymerization.
In particular, in the present invention, it is preferable to add a heat stabilizer in order to improve the whiteness of the obtained molded product. As the heat stabilizer in this case, pentavalent and / or trivalent phosphorus compounds and hindered phenol compounds are preferable.

  Examples of pentavalent and / or trivalent phosphorus compounds include trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite, triphenyl phosphite, phosphoric acid, phosphorous acid, etc. In particular, trimethyl phosphite is preferable. The amount of the phosphorus compound to be added is preferably 2 to 250 ppm as the weight ratio of the phosphorus element contained in the PTT composition. In order to obtain the effect sufficiently, it is preferably 2 ppm or more, and it is 250 ppm or less considering that the polycondensation catalyst is deactivated and the polycondensation rate becomes slow and the desired degree of polymerization cannot be increased. Is preferred. The amount of the phosphorus compound is more preferably 5 to 150 ppm, and still more preferably 10 to 100 ppm as the weight ratio of the phosphorus element.

The hindered phenol compound is a phenol derivative having a substituent having a steric hindrance at a position adjacent to a phenolic hydroxyl group, and a compound having one or more ester bonds in the molecule. Specifically, pentaerythritol-tetrakis (3- (3,5-di-tertbutyl-4-hydroxyphenyl) propionate), 1,1,3-tris (2-methyl-4-hydroxy-5-tert- Butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 3,9-bis (2- (3- ( 3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, 1,3,5 Tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzene) isophthalic acid, triethylglycol-bis (3- (3-tert-butyl-5-methyl 4-hydroxyphenyl) propionate), 1,6-hexanediol-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), 2,2-thio-diethylene-bis ( 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and the like. The amount of the hindered phenol compound to be added is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.5% by weight, and more preferably 0.01 to 0% by weight as a weight ratio to the obtained polymer. More preferably, 1% by weight.
Of course, a combination of two or more of these heat stabilizers is also a preferred method.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
The main measurement values in the examples were measured by the following methods.
(1) Color tone (L value, b * value)
Measurement was performed using a color computer of Suga Test Instruments Co., Ltd.
Moreover, after heating a polymer at 180 degreeC for 20 hours in air atmosphere, the color tone was measured like the above and it was set as the coloring index at the time of a heating.
(2) Acrolein and allyl alcohol content 1 g of a sample was finely cut, put into 10 ml of hexafluoroisopropanol, and dissolved by applying ultrasonic waves. 10 ml of water was added to the solution to reprecipitate the polymer component, and acrolein and allyl alcohol in the supernatant were analyzed using a gas chromatograph / mass spectrometer under the following conditions.
Column: VOCOL (60 m × 0.25 mmφ × film thickness 1.5 μm)
Temperature conditions: 35 to 100 ° C. (temperature rising at 5 ° C./min), then 100 to 220 ° C.
(Temperature rise at 20 ° C / min)
Inlet temperature: 220 ° C
Injection method: Split method (split ratio = 1: 30), 1 μl injection Measurement method: SIM method (3) Crystallinity Density gradient tube made of carbon tetrachloride and n-heptane based on JIS-L-1013 Using the density obtained by the density gradient tube method, it was obtained according to the following formula.
Xc = {ρ _c × (ρ _s −ρ _a )} / {ρ _s × (ρ _c −ρ _a )} × 100 (%)
However,
ρ _a : Amorphous density (g / cm ³ ) = 1.300 g / cm ³
ρ _c : Crystal density (g / cm ³ ) = 1.431 g / cm ³
ρ _s : density of the composition (g / cm ³ )
(4) Intrinsic viscosity [η]
The intrinsic viscosity [η] is extrapolated from the specific viscosity ηsp to the concentration C (g / 100 milliliters) ηsp / C in an o-chlorophenol at 35 ° C. using an Ostwald viscometer. Sought according to.
[Η] = lim (ηsp / C)
C → 0
(5) Carboxyl end group concentration 1 g of the polymer was dissolved in 25 ml of benzyl alcohol, and then 25 ml of chloroform was added, followed by titration with a 1/50 N potassium hydroxide benzyl alcohol solution. The titration value VA (ml) and the polymer were It calculated | required according to the following formula | equation from the blank value VO in the absence.
Carboxyl end group concentration (meq / kg) = (VA-VO) × 20

Example 1
Using DMT and TMG as raw materials, 1000 kg of PTT polymer was polymerized per day by the continuous polymerization method using the apparatus shown in FIG. The first transesterification reactor 1 and the second transesterification reactor 5 are a vertical stirring reactor having a vent port 3 or 7 and a turbine-like stirring blade 2 or 6, and the first polycondensation reactor 9 is vented. A vertical stirring reactor having a port 11 and an anchor-like stirring blade 10 is used, and a horizontal type having a vent port 15 and a uniaxial disk-shaped stirring blade 14 is used in a second double condensation reactor (final polymerization reactor) 13. A stirred reactor was used.
In the polymerization, first, 0.1 wt% of titanium tetrabutoxide with respect to DMT, TMG and DMT at a molar ratio of 1: 1.5 was continuously added to the first transesterification reactor and stirred at normal pressure and 190 ° C. The transesterification reaction was carried out while stirring with the blade 2 and extracting methanol as a by-product from the vent port 3. Next, the solution was sent to the second transesterification reactor 5 by the transfer pump 4 and the transesterification reaction was completed in the same manner at normal pressure and 230 ° C.
Thereafter, the solution is fed to the first polycondensation reactor 9 by the transfer pump 8 and stirred with the stirring blade 10 at 250 ° C. under reduced pressure (3000 Pa), and polycondensation is performed while extracting by-product TMG and the like from the vent port 11. To obtain a polymer having a low polymerization degree. Next, the solution was sent to the second double condensation reactor 13 by the transfer pump 12 and polycondensation was performed in the same manner at 260 ° C. under reduced pressure (100 Pa) to increase the degree of polymerization of the polymer. At this time, 20 ppm of trimethyl phosphate was continuously added to the obtained polymer from between the liquid feed pump 8 and the first polycondensation reactor 9. The catalyst was used as it was added during the transesterification reaction.
The polymer having a higher degree of polymerization was discharged from the discharge port 16 of the second double condensation reactor 13 and then discharged from the spinning port 19 in a strand through a discharge pump 17 and an extraction pipe 18. The cooled and solidified polymer 20 was cooled and solidified in the air and with a water-cooled bath 21 and then cut into pellets by a pelletizer (chip cutter) 22.
At this time, the average residence time from the discharge port 16 to the discharge from the spinning port 19 was 15 minutes. Moreover, the discharge pump 16, the extraction piping 18, and the spinning nozzle 19 were all heated with a 260 degreeC heating medium, and the temperature of the inner wall surface was 255-260 degreeC. Here, the average residence time is obtained from the internal volume of the piping and apparatus existing from the outlet 16 to the outlet 19 and the amount of discharged polymer, and the inner wall temperature is the main part of the piping and apparatus where the heat medium enters and exits. The sensor was placed on the part and measured.
The results are shown in Table 1. The obtained composition pellets were excellent in whiteness with a b * value of 6 and L * of 85, and even when heated in an air atmosphere at 180 ° C. for 20 hours, the b * value was 12 and there was little coloration. Further, the contents of acrolein and allyl alcohol were small, and the crystallinity was within the scope of the present invention. Furthermore, the carboxyl end group concentration was as low as 18, which was a slight increase of 8 meq / kg as compared with the composition collected at the outlet 16.
The obtained pellets were dried in a nitrogen atmosphere at 130 ° C. for 5 hours, and then a Nissei Resin Co., Ltd. PS40E was used as a device, the cylinder set temperature 250 ° C., the mold set temperature 95 ° C., injection 17 seconds, A box-shaped molded product was prepared under injection molding conditions of cooling for 20 seconds. The obtained molded product was excellent in whiteness with a uniform color tone and b * of 8 and L * of 85.

Examples 2-6
Except for the conditions shown in Table 1, polymerization was carried out in the same manner as in Example 1 to obtain pellets. The results are shown in Table 1. In any case, the color tone was excellent, the coloring during heating was small, the contents of acrolein and allyl alcohol were small, and the crystallinity was within the range of the present invention. Further, the carboxyl end group concentration was low, and it was only slightly increased compared to the composition collected at the outlet 16.

Example 7
A reactor for polymerizing while dropping the polymer 27 along the support 27 shown in FIG. 2 using a low polymerization degree PTT polymer having an intrinsic viscosity [η] of 0.5 dl / g and a carboxyl end group concentration of 10 meq / kg. Polymerized 1000 kg of PTT polymer per day. For the polymerization, a low polymerization degree polymer is supplied from a raw material supply port 25 to a polycondensation reactor (final polymerization reactor) 23 by a transfer pump 24, and is supported at an amount of 30 g / min per support in a molten state at 260 ° C. While being along the body, TMG and the like by-produced at a reduced pressure of 100 Pa were polymerized while being extracted from the vent port 26. As the support, a jungle gym-shaped member in which stainless steel wires having a diameter of 3 mm were combined at intervals of 30 mm in the vertical direction and 50 mm in the horizontal direction was used. The discharge pump was operated so that the polymer hardly accumulated at the bottom of the polymerization vessel. As the low polymerization degree PTT polymer, 0.1% by weight of titanium tetrabutoxide / polymer and 100 ppm / polymer of trimethyl phosphate as a weight ratio of phosphorus element were used.
The polymerized polymer was discharged from the discharge port 28 and then discharged from the spinning port 31 through the discharge pump 29 and the extraction pipe 30 into a strand shape. The cooled and solidified polymer 32 was cooled and solidified in the air and in a water-cooled bath 33, and then cut into pellets by a pelletizer (chip cutter) 34. At this time, the average residence time from the discharge port 28 to discharge from the spinning port was 10 minutes. Further, the discharge pump 29, the extraction pipe 30, and the spinning nozzle 31 were all heated with a heat medium of 263 ° C., and the temperature of the inner wall surface was 255 to 260 ° C. Here, the average residence time is obtained from the internal volume of the piping and apparatus existing from the outlet 28 to the outlet 31 and the amount of discharged polymer, and the inner wall temperature is the main part of the piping and apparatus where the heat medium enters and exits. The sensor was placed on the part and measured.
The results are shown in Table 1. The obtained pellets were excellent in color tone, had little coloration upon heating, had low contents of acrolein and allyl alcohol, and had crystallinity within the scope of the present invention. Further, the carboxyl end group concentration was low, and it was only slightly increased compared to the composition collected at the outlet 16.

Example 8
Except for the conditions shown in Table 1, polymerization was carried out in the same manner as in Example 7 to obtain pellets. The results are shown in Table 1. The obtained pellets were excellent in color tone, had little coloration upon heating, had low contents of acrolein and allyl alcohol, and had crystallinity within the scope of the present invention. Further, the carboxyl end group concentration was low, and it was only slightly increased compared to the composition collected at the outlet 16.

Comparative Examples 1-2
Polymerization was carried out in the same manner as in Example 1 except for the conditions shown in Table 1. The results are shown in Table 1.
In the case of Comparative Example 1, the extraction piping from the discharge port 16 to the spinning port 19 is long and thick, so that the average residence time is too long, and the obtained pellets are not only slightly colored, but also 180 ° C., When heated in an air atmosphere for 20 hours, it was intensely colored.
In the case of Comparative Example 2, since the temperature of the heat medium for heating the piping and the apparatus from the discharge port 16 to the spinning port 19 was high, the inner wall surface temperature became too high, and the obtained pellets were only slightly colored. However, when heated at 180 ° C. in an air atmosphere for 20 hours, it was intensely colored.

  The PTT composition of the present invention has an excellent color tone when melt-molded, and can always obtain a molded product having the same color tone, and can be produced with high industrial productivity.

Claims (5)

50 mol% or more is composed of trimethylene terephthalate repeating units, and the remaining 50 mol% or less is composed of other copolymerization components, characterized by satisfying the following requirements (A) to (C) A process for producing a polytrimethylene terephthalate composition comprising:
Using one or more reactors, raw materials, intermediates and low polymerization degree polymers were continuously added to the reactor and reacted in a molten state to continuously produce polytrimethylene terephthalate. Including the continuous withdrawal of the polymer , including the residence time in the flow path in the piping and equipment through which the polymer passes after leaving the final polymerization reactor where the polymer in the molten state undergoes polycondensation at reduced pressure. The polytrimethylene is characterized in that the average residence time until cooling and solidification is 0.01 to 50 minutes, and the temperature of the inner wall surface of the pipe and / or the apparatus in contact with this is 290 ° C. or less A method for producing a terephthalate composition.
(A) The b * value is −5 to 25 and the b * value after heating at 180 ° C. for 20 hours in an air atmosphere is −5 to 25;
(B) Acrolein and allyl alcohol in a solution of the composition dissolved in hexafluoroisopropanol are both 20 ppm / composition or less; and (C) Crystallinity Xc is 0 to 40%.
Here, the crystallinity Xc is
Xc = {ρ _c × (ρ _s −ρ _a )} / {ρ _s × (ρ _c −ρ _a )} × 100 (%)
Represented by
ρ _a : Amorphous density = 1.300 g / cm ³
ρ _c : crystal density = 1.431 g / cm ³
ρ _s : density of the composition (g / cm ³ )   The process for producing a polytrimethylene terephthalate composition according to claim 1, wherein the intrinsic viscosity [η] of the obtained polytrimethylene terephthalate composition is 0.4 to 3.0 dl / g.   The production of a polytrimethylene terephthalate composition according to claim 1 or 2, wherein the carboxyl end group concentration of the polymer which increases from the time of leaving the final polymerization reactor until it is cooled and solidified is in the range of 0 to 30 meq / kg. Method.   The pellet containing the polytrimethylene terephthalate composition obtained with the manufacturing method in any one of Claims 1-3.   A molded article having a b * value of -5 to 25, comprising the polytrimethylene terephthalate composition obtained by the production method according to claim 1.

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